1. Field of the Invention
This invention relates to switches for electric power distribution systems and, more particularly, to electrically powered operators for interlocking the operation of a pair of switches, such as those in a transfer switch.
2. Background Information
Transfer switches commonly used to connect alternate power sources to a load, including networks, utilize a pair of switches each connecting one of the sources to the load. In order to prevent connecting unsynchronized sources together, the operation of the two switches is coordinated, typically by a mechanical interlock, so that only one switch at a time can be turned ON. In many instances, it is desirable to operate the transfer switch remotely. Typically, electric motors have been used to operate the interlocks on transfer switches. The motor powered interlocks operate relatively slowly so that there is a noticeable dead period between the time that one of the switches is turned OFF and the other is turned ON. It is desirable to minimize this dead period while assuring that the two switches are never both ON at the same time.
U.S. Pat. No. 4,553,115 describes a solenoid powered operator for a single, molded case circuit breaker. This device operates the circuit breaker handle rapidly each time the solenoid is energized. It would be desirable to be able to operate the pair of switches in a transfer switch at a similar rapid rate, thereby reducing the interval in which the load is unenergized.
There is a need, therefore, for an improved operator for the switches of a transfer switch which allows the transfer to be made more rapidly.
This need, and others, are satisfied by the invention which is directed to a fast acting, electrically powered operator for a pair of electric power switches and to a transfer switch incorporating this operator. The switches of a transfer switch are mounted end to end with their handles oppositely reciprocable in a common plane between OFF and ON positions. The electrically powered operator comprises a solenoid, and a mechanical assembly coupling the solenoid to the handle of the first switch for reciprocating the handle between the ON and OFF positions on successive actuations of the solenoid. A coupling comprising an elongated member couples the handle of the second switch to the handle of the first switch for movement therewith to reciprocate the handle of the second switch between the OFF position and the ON position opposite to the ON position and OFF position of the handle of the first switch.
The solenoid is a single action solenoid having an electromagnet and an armature movable relative to the electromagnet. The mechanical assembly includes a first drive member coupled to the electromagnet and a second drive member coupled to the armature. A latch mechanism reciprocates between a first latch position in which the first drive member is held fixed and the second drive member moves upon actuation of the single action solenoid, and a second latch position in which the second drive member is held fixed and the first drive member moves upon actuation of the single action solenoid. A first yoke engages the first handle to reciprocate the first handle between the ON and OFF positions on successive actuations of the single action solenoid through alternate engagement by one and then the other of the first and second drive members. The first yoke engages and toggles the toggle mechanism as the first handle reciprocates between the ON and OFF positions. The elongated member of the coupling is coupled to the first yoke. A second yoke connects the elongated member to the second handle. The coupling includes a guide mounted on the second switch guiding the reciprocal movement of the elongated member and maintaining the second yoke in engagement with the second handle. The mechanical assembly includes a frame mounted on the first switch and within which the first and second drive members reciprocate. The frame includes a guide in the form of a slot for guiding reciprocal movement of the elongated member and maintaining the elongated member in engagement with the first handle through the first yoke.
The invention also embraces the fast acting, electrically powered operator for a pair of end mounted electric power switches.